TWI506078B - A hardenable two part acrylic composition - Google Patents

Description

Hardenable two-component acrylic composition

The present invention relates to a polymer composition, particularly, but not exclusively, to a hardenable two-component acrylic composition, a polymer component of the two-component hardenable composition, and a polymer for making the two-component composition The method of ingredients.

The hardenable composition formed by mixing an acrylic polymer with a monomer is suitable for many applications. Especially used in dental, medical, adhesive and architectural applications, these materials have been used in these applications for more than 40 years.

Dental applications include for dentures, denture holders, denture liners, denture repairs, custom trays, inlays for crowns and bridges, artificial teeth, inlays and repairs for natural teeth, and dental restorations .

Medical applications include use as a bone cement. Bone adhesives are generally used for filling bone cavities and, in particular, for use as prosthetic adhesives, skull adhesives, vertebral adhesives in vertebroplasty, and for the manufacture of shaped articles which are hardened in vitro and which can then be introduced into the body.

Adhesives and architectural applications include numerous applications such as bonding, bonding, caulking, and forming porous materials.

The curable acrylic composition generally consists of a solid component and a liquid component. The solid component comprises a powder formed from polymer particles and, if appropriate, other additives such as polymerization initiators and catalysts, fillers and dyes. The liquid component comprises a liquid monomer and other additives such as accelerators and stabilizers. When ready for use, the solid component is mixed with the liquid component to form a liquid or semi-solid slurry which increases in viscosity and hardens into a solid under the action of a polymerization initiator and an accelerator.

The solid components usually used consist of small spherical beads of poly(methyl methacrylate) (PMMA) (typically about 20-150 microns in diameter) and a small amount of polymerization initiator (such as benzamidine peroxide (BPO)). The initiator is typically encapsulated within the PMMA beads, but may also be added as a separate component. The liquid component is typically a monomer, typically methyl methacrylate (MMA), which may also contain a polymeric activator such as N,N-dimethyl-p-toluidine (third amine) (DMPT) and such as hydroquinone ( An inhibitor of HQ) to prevent spontaneous polymerization of the monomer.

When the solid component is mixed with the liquid component, the polymer particles are wetted by the monomer, solvated and begin to dissolve. The solvated polymer particles release the benzammonium peroxide initiator to the monomer that interacts with the activator, if present, to produce a free reaction with the monomer and initiate polymerization of the monomer at room temperature. base. The mixture starts with a relatively low viscosity and develops into a system that is getting harder and harder and eventually hardens.

This changing mixture viscosity is characterized by paste time, working time and set time. The bake time is considered to be the length of time after which the mixture begins to mix to form a mass which does not adhere or adhere to the polypropylene mixing beaker wall and can be removed in one piece using a spatula. The setting time is determined by forming the dough into a sausage shape and intermittently tapping the hard surface with it. The setting time is regarded as the time from the start of mixing until the mixture is converted into a hard block which does not deform and which has a significant change in the sound produced when the hard surface is lightly rubbed. This working time was determined by intermittently moving the two masses together and pulling them apart. Make a note of the time when the two masses no longer stick together. Working time is calculated by subtracting the maturing time from the time it takes to mix the two masses to the point where they do not stick together.

Pasting time, working time and setting time are extremely important parameters for determining how to use the hardenable composition. The hardenable compositions at room temperature (so-called "self-curing" or "low temperature curing" systems) have a bake time of typically 4 to 10 minutes and a set time of usually 10 to 25 minutes. The working time effectively defines the period of time during which the operator can operate the mass in the desired manner, such as pressing into a denture mold for the manufacture of a denture, or pressing into the bone cavity during hip repair or replacement, or injecting a vertebral cavity during spinal surgery. Medium, or forced into the gap or cavity during industrial bonding operations. It is obviously desirable to maximize the working time available to the operator. This should theoretically be achieved without increasing the setting time, since the setting time defines the end of the bonding or fixing operation. Therefore, focus on shortening the time of maturity. The bake time is determined by the rate at which the combination of solid and liquid components is immediately increased after mixing and is controlled by a number of factors such as polymer bead size and shape, polymer molecular weight, and polymer composition. .

US 5,650,108 (Nies et al.) describes the use of a bead mill to treat a mixture of PMMA beads and granules. The resulting polymer mixture was then stirred with the liquid ingredients to give a composition which was agglomerated after about 2 minutes.

US 2007/0213425 A1 (Higham and He) teaches the use of a ball mill or a jet mill to produce ground PMMA or PMMA copolymer beads which exhibit a paste blend with the liquid component of the bone binder as compared to the unground beads. The cooking time is shortened.

US 4,268,639 (Seidel et al.) describes the use of PMMA as a solid component and poly(2-hydroxyethyl methacrylate) (PHEMA) with MMA as a liquid component and/or 2-hydroxyethyl methacrylate (HEMA). A fast agglomerated self-curing composition of the mixture. Describe the cooking time as short as 2 minutes and working time of at least 6 minutes.

US 2007/0032567 A1 (Beyar et al.) describes a fast agglomerated bone cement that achieves a viscosity of at least 500 Pascal seconds and a working time window of at least 5 minutes within 180 seconds after mixing the monomer component with the polymer component. combination. These features are said to be obtained by using beads having different size distributions. Beads having a diameter of less than 20 microns are said to contribute to rapid wetting through the monomer liquid and promote rapid transition to a viscous state.

The effect of PMMA bead size on the rheological properties of bone cements has been investigated by Hernandez, L.; Goni, I.; Gurruchaga, M., "Effect of size of pmma beads on setting parameters and rheological properties of injectable Bone cements", Transactions-7th World Biomaterials Congress, Sydney, Australia, May 17, 2004 - May 21, 2004, page 740. The authors point out that "as the fraction of small beads increases... the viscosity increase seems to start faster. This is due to the solvation of the smallest PMMA beads (less than 20 microns), which increases the viscosity of the polymeric block." . Also, "Finally, it can be said that it is feasible to obtain an injectable bone adhesive having optimum rheological properties by mixing beads of different sizes."

Another article describing how the rheological properties of acrylic bone binders are affected by PMMA bead size is: Lewis G. and Carroll M, J Biomed Mater Res (Appl Biomater) 63:191-199, 2002. The authors conclude that one of the factors that strongly influence rheological properties is the relative amount of small-sized PMMA beads (average diameter between 0 and 40 microns).

A study on the maturing time of heat-cured dental resins (McCabe, JF, Spence D. and Wilson HJ, Journal of Oral Rehabilitation, 1975, Vol. 2, pp. 199-207) concluded that "...short paste The concept of cooked time depends on the presence of a large number of small beads." It is inferred that the particle diameter D of the small beads is less than 20 microns.

As can be seen from the above description, the most commonly described method for achieving short bake time is to grind PMMA polymer particles or intentionally incorporate a large proportion of PMMA polymer particles having a diameter of less than 20 microns into the solid component of the hardenable composition. . The grinding method has a limited amount of beads that can be ground at one time, resulting in a disadvantage of a long manufacturing time when a large amount of material is involved. In addition, the following problems need to be overcome: reproducibility between batches, cleaning of the grinder between batches, and introduction of contamination during bulk processing and manual operations. Controlling the relative amount of PMMA polymer particles having a diameter of less than 20 microns in the solid component is not straightforward. The PMMA beads used in the hardenable composition are typically made by suspension or dispersion polymerization processes. This involves polymerizing droplets of MMA monomer dispersed in a liquid phase (usually water) to form solid spherical beads, which are then separated from the liquid phase by a filtration step, washed to remove the dispersant, dried and Then sieved. However, particles less than 20 microns in diameter are relatively difficult to filter and wash, which involves longer and often more cumbersome processing times.

An alternative to collecting a large proportion of small (less than 20 microns in diameter) PMMA polymer particles is to separate the smallest particle size fraction from the conventionally prepared suspension polymerization slurry using a sieving process. However, the problem is relatively low, the sieving time can be long and the problem of how to handle a relatively large amount of coarser-grained material remaining on the screen still exists.

Another method of producing a large proportion of small (less than 20 microns in diameter) PMMA polymer particles is to use mechanical methods to decompose beads of conventionally manufactured materials, such as by grinding, milling, crushing, and the like. However, PMMA beads are relatively hard and typically require an excessively long processing time to achieve a significant increase in the proportion of small (less than 20 microns in diameter) PMMA polymer particles (usually longer than 24 hours for ball milling). In addition, the inter-batch repeatability of such a process is rather poor, and sometimes the resulting product needs to be further processed (e.g., by sieving or blending) to achieve the desired particle size distribution.

This makes it commercially expensive to manufacture PMMA with a large proportion of particles less than 20 microns in diameter that becomes expensive and sometimes lengthy and unreliable.

It is an object of the present invention to provide an alternative to avoiding one or more of the above problems.

According to a first aspect of the present invention, there is provided a hardenable two-component acrylic composition comprising a first component of an acrylic polymer composition and a second component of an acrylic monomer composition, the acrylic polymer composition comprising the first A type of acrylic polymer particle characterized in that each of the first type of acrylic polymer particles is formed from a network of coalesced emulsion polymerized acrylic particles.

Coalescence does not mean that the individual particles are completely combined, but are sufficiently joined together to form a larger first type of particle. Typically, the particles are in intimate contact and retain individual features.

Preferably, the acrylic polymer composition also comprises at least one other type of acrylic polymer particles. Preferably, the at least one other type of acrylic polymer particles are polymer beads. The beads are not formed from a network of coalesced emulsion polymerized particles, but are preferably produced by conventional polymer processing. Such polymeric beads are well known to those skilled in the art of acrylic polymer compositions and can be prepared, for example, by bulk polymerization, solution polymerization or suspension polymerization. Generally, the beads are prepared by polymerization of a suspension. More than one other type of acrylic polymer particles may be present in the acrylic polymer composition which are distinguished from each other by an average particle size and/or molecular weight. For example, two, three or four such other types of acrylic polymer particles may be present.

The term beads as used herein, unless otherwise indicated, is not intended to be interpreted in a limiting manner and refers to discrete polymeric particles having any suitable size, shape, and surface texture.

Typically, the total amount of the first type of polymer particles and, if present, other types of polymer particles constitute at least 98% of the polymer present in the acrylic polymer composition, more preferably in the acrylic polymer composition. At least 99%, preferably about 100%, of the polymer present. The total amount of the first type of polymer particles and, if present, other types of polymer particles generally constitutes from 50 to 99.9% w/w, more preferably from 60 to 97.5% w/w, of the acrylic polymer composition, preferably It is 65-94.5% w/w. The remainder is typically comprised of fillers, dyes, catalysts, and initiators, however, residual emulsifiers may also be present.

Typically, the amount of filler in the acrylic polymer composition is from 0 to 49.9% w/w, more preferably from 2-39.9% w/w, most preferably from 5 to 34.9% w/w, of the acrylic polymer composition. The total content of residual or added unreacted initiator in the acrylic polymer composition is usually from 0.1 to 5.0% w/w, preferably from 0.2 to 4.0% w/w, more preferably from 0.4 to 3.5, based on the acrylic polymer composition. % w/w.

The initiator may be present in the first type of polymer particles forming the acrylic polymer composition and, if present, in other types of polymer particles. The first polymer particles and, if present, the initiator in the other polymer particles are residual amounts of unreacted initiator used to form the particles, and thus are equivalent to excess initiator. Alternatively or additionally, some of the initiator may be added to the two-component composition as a separate component. In the emulsion-polymerized acrylic fine particles, the residual initiator present before the reaction with the second component is usually 0.001 to 10.0% w/w, preferably 0.1 to 5.0% w/w, more preferably 0.1 to 5.0% w/w. It is 0.1-3.0% w/w. Alternatively, the content of the initiator is preferably from 0.1 to 6.0% w/w, more preferably from 0.1 to 5.0% w/w.

As determined by light scattering using a Malvern Zetasizer Nano Series S Particle Size Analyzer (add a drop of emulsion to 1 ml of deionized water in a measuring cuvette, equilibrate the test sample at 25 ° C and use the software provided by the instrument The Z average particle size is determined to form a coalesced network to form emulsion polymerized microparticles of the larger acrylic polymer particles of the present invention having a Z average particle size of preferably less than 2000 nm, more preferably less than 1000 nm, most preferably less than 800 nm, especially less than 500 nm. The emulsion-polymerized microparticles preferably have a Z average particle size ranging from 10 to 2000 nm, more preferably from 20 to 1000 nm, most preferably from 50 to 500 nm, especially from 150 to 450 nm, as determined by light scattering using a Malvern Zetasizer as described above.

Generally, the emulsion-polymerized microparticles may be single-stage or multi-stage microparticles, that is, so-called core/shell microparticles. In this regard, it may be appropriate to use a single monomer such as methyl methacrylate to prepare the seed crystal, core and shell. In this case, especially if the composition and molecular weight of the seed crystal, core and shell are designed to be the same, a standard one-stage emulsion polymerization technique known to those skilled in the art can be used. However, in order to obtain emulsion particles which exhibit a certain control over the structure, especially composition, particle size and molecular weight, a multi-stage core-shell emulsion polymerization process is preferably used.

For the production of core-shell particles by emulsion polymerization, it is preferred to employ a method widely used in which seed particles are initially formed, which then serve as crystal nuclei for further growth, that is, to produce a polymer core and then to produce a shell. The concept is described in more detail by VLDimonie et al., "Emulsion Polymerization and Emulsion Polymers", edited by PA Lovell and MS El-Aasser, John Wiley & Sons Ltd, Chapter 9, pages 294-326, (1997). ). Seed particles can be formed and stabilized using an emulsifier free technique (i.e., using an ionic water-soluble initiator such as potassium persulfate, sodium persulfate or ammonium persulfate to stabilize the particles) or stabilized by the use of an emulsifier. After the seed particles are formed, the core and the shell are formed by sequentially adding the monomer and other aliquots of the initiator.

In a particularly preferred embodiment, the emulsion microparticles are in their polymer matrix with an initiator. Thus, in this embodiment, the initiator is not independently added to the polymer particles of the first type of the invention.

Advantageously, the initiator of the hardenable composition may be added in the form of an excess of initiator during the emulsion polymerization of the microparticles such that some of the initiator is used for the polymerization of the emulsion particles, and when the emulsion particles are formed, the excess initiator is incorporated into the polymer. In the matrix. Subsequently, after wetting and dissolution by the monomer, the initiator is released and thus it is able to initiate a hardening period. In the core/shell particles, the initiator is preferably incorporated into the outer shell, i.e., incorporated in the final stage of the multi-stage emulsion polymerization process, and thus excess initiator is used in the final shell polymerization stage. More than one initiator may also be used during the polymerization of the first type of polymer particles or other types of polymer particles. It is advantageous in the case of a plurality of initiators that one initiator is substantially depleted in the polymerization and the second initiator is in excess and only partially used to cause an excess of the second initiator to be incorporated into the particles. This procedure can be used to maximize the half-life of the initiator (i.e., the initiator with a higher rate of decomposition at a particular temperature and in a particular reaction medium) with the help of initiators having different half-lives. Additionally, higher temperatures can be used to promote polymerization in the presence of the first initiator, while lower temperatures can delay polymerization of the monomer in the presence of the second initiator to be the residual initiator. However, since some of the polymerization must be carried out in the presence of the second initiator in order to incorporate the second initiator into the particles, some of the second initiator will inevitably be used up. Whether using one or more initiators, the amount of initiator remaining as a residue depends on the time the initiator is exposed to the polymerization conditions and the reactants and, if present, the relative reactivity of the first initiator. Those skilled in the art will appreciate that the exact amount of residual initiator will depend on the experimental conditions and can be readily determined by trial and error and then reproducible by careful control of the amount of monomer and initiator and processing conditions. The time to add excess initiator is also related to the molecular weight of the polymer. If added prematurely in the polymerization, the molecular weight of the particles will decrease. Thus, the desired molecular weight will also affect the time during which an excess of initiator is added to allow for the incorporation of excess initiator while achieving the molecular weight required for a particular application.

For the avoidance of doubt, "excessive initiator" means an initiator portion that is not required for the polymerization of the acrylic polymer particles and which can be used in subsequent reactions after terminating the initial polymerization of the acrylic polymer particles.

Advantageously, the network of coalesced emulsion polymerized microparticles forms porous acrylic polymer particles, more preferably microporous acrylic polymer particles.

In the present invention, micropores mean that the average pore diameter is between 0.1 nm and 2000 nm, more preferably between 1 and 1000 nm, and most preferably between 10 and 500 nm. The pore size can be determined by scanning electron microscopy (SEM) according to the following test method: A sample of acrylic polymer particles is sprayed onto a conductive self-adhesive carbon tab on a standard aluminum SEM stage. The sample was coated with a thin layer of metal (Pt) by vacuum metallization to avoid charging in the SEM instrument. SEM images were acquired using a Hitachi S4500 field emission SEM using an acceleration voltage of 3 kV and a working distance of 20 mm. Several particles were imaged and representative images were obtained at different magnifications.

In general, it is believed that the size of the first type of acrylic polymer particles of the present invention is not critical, but will obviously exceed the size of the emulsion particles. Typically, the first type of acrylic particles of the present invention have an average particle size of from 1 to 300 microns, more typically from 2 to 200 microns, and most typically from 5 to 200 microns, especially from 5 to 150 microns. However, it is believed that the size of the particles of the present invention is not critical to the emulsion polymerized microparticles that make up their structure. Surprisingly, the use of the first type of acrylic polymer particles in the hardenable composition results in a shortened paste time.

Generally, the first type of acrylic polymer particles of the present invention are formed by drying a liquid emulsion to form a powder.

A preferred way of drying the emulsion polymer particles is to use spray drying. However, other methods of directly drying the emulsion polymer may also be present, such as vacuum paddle drying or spin drying. Further, the emulsion may be agglomerated by using an ionic salt such as magnesium sulfate, calcium chloride, aluminum sulfate or the like, followed by filtration, washing and drying. All of this technique will cause the emulsion particles to coalesce into larger particles. Surprisingly, it has been found that the use of such larger particles in the hardenable composition significantly reduces the bake time. It has not been expected that the use of such formed particles will cause such an improvement. The coalescence of the emulsion particles does not cause them to completely merge, but instead forms a network of joined particles. These drying techniques and pre-emulsion polymerization allow for extremely careful control of the size of the microparticles and the first type of particles, which makes reproduction easier and reduces batch-to-batch variations.

Drying means reducing the moisture content of the emulsion particles to less than 10% w/w, more preferably less than 5% w/w, most preferably less than 2% w/w.

If more than one type of acrylic polymer particles are present, the different types of polymer particles are typically blended together to form an acrylic polymer composition in the presence of other suitable polymer composition components known to those skilled in the art. . These polymeric composition additives include initiators, catalysts, dyes, and fillers.

Blending the polymer particles of the first type of the invention with other polymer particles can be carried out by any technique known to those skilled in the art to be suitable for blending particles of different sizes.

However, a preferred manner of blending small polymer particles with larger polymer particles is by conventional inversion blending. Other methods of blending the powder, such as screw blending and roll blending, may also be present.

The initiators which can be used to initiate the emulsion polymerization are persulfates (such as potassium persulfate, sodium persulfate or ammonium persulfate), peroxides (such as hydrogen peroxide, benzamidine peroxide, and tert-butyl hydroperoxide). , a third amyl hydroperoxide, di(2-ethylhexyl)peroxydicarbonate or lauric acid peroxide, and an azo initiator (for example, 4,4'-azobis(4-cyano) Valeric acid)).

An initiator is also present in the polymer composition to initiate the hardening process. In addition to the above emulsion initiators, a particularly preferred initiator at this stage is benzoxide peroxide.

Emulsifiers useful in emulsion polymerization are typical emulsifiers in conventional emulsion polymerization, including anionic emulsifiers (eg, sodium dioctyl sulfosuccinate, ethoxylated alcohol half esters of sulfosuccinic acid) , sodium N-(1,2-dicarboxyethyl)-N-octadecylsulfosuccinate, sodium sulfated alkylphenol ethoxylate, sodium alkane sulfonate, dodecyl Sodium sulphate or sodium 2-ethylhexyl sulphate, nonionic emulsifier (eg polyethylene glycol nonylphenyl ether, polyoxyethylene octyl phenyl ether or difunctional ethylene oxide / propylene oxide block copolymer) Or a cationic emulsifier (such as cetyltrimethylammonium bromide or alkyl polyglycol ether ammonium methyl chloride). Reactive or polymerizable emulsifiers or surfactants suitable for use with acrylic emulsions, such as sodium dodecyl sulfosuccinate, sodium styrene lauryl sulfonate, ten, may also be used. Methyl acrylate or vinylbenzyl macromonomer or bromomethacryl oxime of sodium dialkyl ethyl sulfonate, methacrylamide, polyethylene oxide or ethylene oxide/propylene oxide block copolymer Ethyl hexadecyldimethylammonium.

The resulting emulsion-polymerized microparticles preferably have a Z average particle size of less than 2000 nm, more preferably less than 1000 nm, most preferably less than 800 nm, especially less than 500 nm, as determined by light scattering. The Z-average particle size of the emulsion-polymerized microparticles is preferably in the range of from 10 to 2000 nm, more preferably from 20 to 1,000 nm, most preferably from 50 to 500 nm, especially from 150 to 450 nm, as determined by light scattering.

The core-shell ratio (C:S) of the emulsion particles is usually between C:S 95:5 (% by weight) and C:S 40:60 (% by weight), more usually between C:S 90:10 ( Between the weight %) and C:S 50:50 (% by weight), preferably between C:S 85:15 (% by weight) and C:S 70:30 (% by weight).

The solids content (% by weight) of the pre-drying emulsion is generally between 5% and 45% by weight, more usually between 7.5 and 40% by weight, preferably between 10% and 37.5% by weight. .

The weight average molecular weight (Mw) of the emulsion microparticles is typically between 25,000 daltons and 3,000,000 daltons, more typically between 100,000 daltons and 1,500,000 daltons, preferably between 250,000 daltons. Between 1,000,000 Daltons, for example between 250,000 Daltons and 600,000 Daltons. For this purpose, the molecular weight can be determined by gel permeation chromatography (GPC).

Initiators useful for emulsion-free emulsion polymerization include: ionic water-soluble initiators such as potassium persulfate, sodium persulfate or ammonium persulfate.

In medical applications and some dental applications, the filler is preferably an x-ray impermeable filler such that it can be observed by x-rays during treatment or surgery. Suitable fillers for this purpose include barium sulphate and zirconium dioxide, which are encapsulated within the polymer particles or in free form. Other fillers may be used in the manufacture of dentures or in industrial applications and such fillers will be known to those skilled in the art. Additionally, x-ray opaque organic monomers can be used in place of the filler. These monomers can be copolymerized into either acrylic polymer particles or incorporated into the acrylic monomer composition during the manufacture of the acrylic polymer particles. Typical x-ray opaque organic monomers include halogenated methacrylates or halogenated acrylates such as 2,3-dibromopropyl methacrylate or 2-methylpropenyloxyethyl-2,3,5- Triiodobenzoate.

As noted above, the polymer compositions of the present invention can include other types of acrylic polymer particles.

The methods of making such other particles are generally conventional suspension polymerization or dispersion polymerization to produce generally spherical polymer particles or beads. However, other manufacturing methods, such as bulk polymerization or solution polymerization, followed by solvent evaporation may also be present.

The acrylic polymer herein regardless of the first type of acrylic polymer or at least one other type of acrylic polymer independently means, for each type, the homopolymerization of a polyalkyl (alkyl) acrylate or (alkyl) acrylate. a copolymer of an alkyl (meth) acrylate or (alkyl) acrylate with one or more other vinyl monomers. A homopolymer of methyl methacrylate or a copolymer of methyl methacrylate with one or more other vinyl monomers is typically employed. Other vinyl monomers mean another polyalkyl (alkyl) acrylate or (alkyl) acrylate such as ethyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, acrylic acid Third butyl ester, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, 2-ethylhexyl acrylate, lauryl methacrylate , lauryl acrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, methacrylic acid, acrylic acid; hydroxy functional acrylate such as 2-hydroxyethyl methacrylate , hydroxypropyl ethyl methacrylate, 2-hydroxyethyl acrylate or hydroxypropyl acrylate; vinyl compounds such as styrene, vinyl pyrrolidone, vinyl pyridine; and compatible crosslinking monomers, such as Allyl acrylate, divinyl benzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, 1,4-butanediol dimethacrylate, 1,4-butanediol diacrylate 1,6-hexanediol dimethacrylate 1,6-hexanediol diacrylate, in particular compatibility with acrylic crosslinking monomers.

Crosslinking monomers can be used to crosslink one type of acrylic polymer particles. For emulsion polymerized microparticles, crosslinking can be carried out in the core and shell, or only in the core, or only in the shell. Crosslinking achieves the purpose of fine tuning the properties of the hardenable two component acrylic composition.

The acrylic monomer herein means any suitable alkyl (meth)acrylate or (alkyl) acrylic acid such as methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, methacrylic acid or Acrylic acid, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, 2-ethylhexyl acrylate, lauryl methacrylate, lauryl acrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate; hydroxy functional acrylate, such as A 2-hydroxyethyl acrylate, hydroxypropyl ethyl methacrylate, 2-hydroxyethyl acrylate or hydroxypropyl acrylate; vinyl compounds such as styrene, vinyl pyrrolidone, vinyl pyridine; Cross-linking monomers such as allyl methacrylate, divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, 1,4-butanediol dimethacrylate, 1,4 -butanediol diacrylate 1,6-hexanediol dimethacrylate and 1,6-hexanediol diacrylate, in particular compatibility with acrylic crosslinking monomers. Methyl methacrylate is usually used.

The acrylic monomer composition of the present invention is typically one or more of the monomers as defined above and, where appropriate, suitable inhibitors such as hydroquinone (HQ), methylhydroquinone (MeHQ), 2,6-di- Third butyl-4-methoxyphenol (Topanol O) and 2,4-dimethyl-6-tert-butylphenol (Topanol A). Inhibitors are present to prevent spontaneous polymerization of the monomers. Polymeric activators or accelerators, such as N,N-dimethyl-p-toluidine (DMPT) and N,N-dihydroxyethyl-p-toluidine (DHEPT), both of which are third amines, may also be present, Or an organic soluble transition metal catalyst. The presence of an activator or accelerator depends on the final application. Accelerators are often required when "low temperature cure" is necessary (such as in dental applications or bone adhesive applications). However, for industrial applications, heat may also be used in "thermal curing" systems. For example, a denture can be activated by heat.

Alkyl as used herein means C ₁ -C ₁₈ alkyl, wherein the term alkyl/alk encompasses cycloalkyl and hydroxy-functional C ₁ -C ₁₈ alkyl. The alkyl group (alk) herein means a C ₀ -C ₈ alkyl group.

According to a second aspect of the present invention, there is provided a hardenable two-component acrylic composition comprising a first component of an acrylic polymer composition and a second component of an acrylic monomer composition, the acrylic polymer composition comprising acrylic acid polymerized Particles, wherein at least the first type of acrylic polymer particles are microporous particles.

Generally, as described above, the emulsion-polymerized microparticles of the first aspect of the invention are agglomerated by a polymer emulsion of dried particles, such as by spray drying, paddle drying, drying or coacervation, and drying after filtration. Advantageously, spray drying allows for easy control of the final particle size by appropriately varying the spray droplet size. In any case, the drying step causes the emulsion particles to coalesce and form a network of emulsion particles, typically producing larger, porous particles. In general, it has been found that emulsion polymerized particles can coalesce into a loose hexagonal matrix of matrices generally in the same plane, but in the context of the present invention, large pores are created due to the arrangement and the pores and defects in the three-dimensional structure of the particle network. structure. The emulsion polymerized particles are also inevitably present in a small cluster form as well as individual particles in a coalesced network of larger powder particles. However, most of the particles exist as larger particles as part of the coalescing network. For the avoidance of doubt, the free emulsion polymerized particles present which do not form part of such a web are not considered to be the first type of acrylic polymer particles of the invention and, if present, constitute only the first acrylic polymer composition. The remainder of the total polymer present in the component. In any case, the presence of a coalesced network of emulsion polymerized particles results in a surprisingly shortened paste time of the hardenable composition. In addition, this solution provides extremely effective control over paste time so that any other type of particles in the composition can be used to achieve the necessary working time and set time. This means that it is easier to control various parameters because only one particle component is necessary to control the paste time. In prior art systems, it was necessary to use more than one type of particle to control only the paste time, so that simultaneous control of working time and solidification time is extremely complicated. Accordingly, the present invention simplifies the compositions of the prior art.

In a preferred embodiment, the acrylic polymer composition comprises a first type of polymer particles and only a single type of other acrylic polymer particles, the former controlling the paste time and the latter controlling the working time.

According to a third aspect of the present invention, there is provided a hardenable two-component acrylic composition comprising a first component of an acrylic polymer composition and a second component of an acrylic monomer composition, the acrylic polymer composition comprising a particle size The emulsion polymerized acrylic polymer particles between 10 nm and 2000 nm.

The exact size of the emulsion polymerized particles in the larger first type of particles that are coalesced and dried is difficult to determine because it tends to form a matrix with other particles after drying and can form a hexagonal dense arrangement as described above or Other permutations. However, the particles are still clearly defined in their coalescence. Despite this, the particle size of the larger first type of particles is still difficult to determine. However, by examining the SEM results, the size of the particles can be clearly estimated. Typically, the individual coalesced emulsion polymeric particles have an average size of from 10 to 2000 nm, more typically from 50 to 500 nm, and most typically from 150 to 450 nm. As noted above, the emulsion polymerized acrylic polymer microparticles typically coalesce into larger acrylic polymer particles produced by drying the emulsion. Thus, the emulsion particles form microporous particles in their coalescence.

Particles herein are meant to be smaller than particles of the first type of acrylic polymer particles and are not to be construed as having other limitations unless stated herein.

The acrylic polymer composition is generally present in powder form prior to mixing with the monomer composition. Prior to mixing with the monomer components, the powder component generally includes any filler to form the filler into a portion of the dry powder polymer composition. The weight ratio of the powder component to the monomer component is generally less than 3:1, more preferably less than 2.5:1, and most preferably less than 2.2:1. Usually, the weight ratio is in the range of 2.15:1-1.85:1.

According to another aspect of the present invention, there is provided a method of making an acrylic polymer composition comprising the steps of:

(a) subjecting the acrylic monomer composition to emulsion polymerization to produce a polymer emulsion;

(b) drying the polymer emulsion of step (a) to produce acrylic polymer particles according to the first aspect of the invention;

(c) mixing the acrylic polymer particles of step (b) with at least one other type of acrylic polymer particles and/or fillers as appropriate to produce an acrylic acid polymerization suitable for curing at a predetermined rate in the presence of an acrylic monomer composition. Composition.

Preferably, step (a) comprises a seed emulsion polymerization step, a core emulsion polymerization step, and at least one shell emulsion polymerization step. A particularly preferred method introduces an excess of the initiator into the emulsion polymerization step (a) such that the residual initiator is encapsulated within the emulsion particles. Preferably, in the multi-stage emulsion polymerization, an excess of initiator is introduced in the final stage to cause it to be present in the outer shell of the multi-stage particle. Alternatively, however, the initiator may be added after the acrylic polymer composition.

The change in the amount of encapsulated residual initiator or added initiator (e.g., benzamidine peroxide) has the effect of altering the setting time of the hardenable composition. An increase in the initiator content results in a shorter solidification time. Additionally, changes in the amount of accelerator (e.g., DMPT) in the acrylic monomer composition can also affect the setting time. An increase in the accelerator concentration shortens the setting time.

An advantage of the first aspect of the acrylic polymer particles of the present invention is that a fast paste time is achieved in the presence of the acrylic monomer composition. However, the working time and setting time of the dough need to be varied depending on the application. If very short working time and solidification time are required, the acrylic polymer particles of the first aspect of the invention can be used alone. However, in most applications, longer working times and set times will be required and this can be achieved by varying the amount, type and particle size of other types of acrylic polymer particles. It is known that polymer particles having a smaller average particle size (e.g., typically less than 20 microns) also result in shorter working times, but by increasing the amount of particles having a larger particle size and by increasing the particle size itself, a longer working time can be achieved. Accordingly, the particle size and amount of other acrylic polymer particles will depend on the end application and should be understood by those skilled in the art.

Generally, other types of acrylic polymer particles are in the form of solid polymer particles (referred to as polymer beads). As described above, the beads are usually produced by suspension polymerization, however, solution polymerization and bulk polymerization are also possible manufacturing methods. The beads may also contain encapsulated residual initiator as described above for the emulsion polymerized microparticles. Although the average particle size of the beads is variable as described above, the typical average particle size of the beads is from 10 to 1000 microns, more typically from 20 to 250 microns, and most typically from 25 to 125 microns, depending on the final application. Within the scope. The larger the average granularity, the longer the working time. Those skilled in the art should also understand that the molecular weight of the polymer and the presence of the accelerator can also affect working time and solidification time. Therefore, an important aspect of the present invention is that the maturity time can be shortened by the presence of the first type of acrylic polymer particles, and the present invention is not limited to a specific working time or solidification time, since this will depend on the application. .

Although as described above, a particularly advantageous application of the acrylic polymer composition of the present invention is for a bone cement composition. These compositions are used in vertebroplasty and require very short paste times so that the operation can be carried out without undue delay. In addition, such uses require a shorter setting time so that the fixation of the patient's operating site is not unnecessarily extended. The competition requires sufficient working time for the program to be effective. Shortening the time of maturity has the effect of increasing working time. A similar application of the compositions of the present invention is a dental prosthetic application requiring similarly shorter paste times.

However, shorter paste times can be considered to be generally required in many industrial applications and thus the invention is not limited to bone cement applications and dental applications, although such applications are preferred embodiments.

Accordingly, the present invention extends to the use of acrylic polymer particles formed from a network of coalesced emulsion polymerized acrylic microparticles as a bake time shortening agent in a hardenable two component acrylic composition.

The ratio of the first type of acrylic polymer particles of the present invention to all of the other types of acrylic polymer particles will vary depending on the final application. However, in some applications such as bone cements, it is advantageous that the ratio is between 2 to 45:98 and 55 w/w, more preferably between 5 and 35:95 to 65 w/w, most preferably 10-25: 90-75 w/w. This ratio creates a good balance between short paste time and long work time. However, no limitation should be made thereto and there may be other ratios of higher emulsion polymerization particles, such as 100% w/w of emulsion polymerized particles forming the polymer component of the first component, or 30-70:70-30, More usually a ratio of 40-60:60-40.

Emulsion polymerized particles are well known in the art of impact modifiers. To this end, an impact modifier such as butadiene or butyl acrylate is typically introduced into a shell of the multistage core-shell particles in the form of a comonomer. However, in the hardenable composition of the present invention, an impact modifier may not be required. Thus, the emulsion microparticles of the present invention may be free of impact modifier comonomer residues.

While the molecular weight of the polymer in the polymer powder component of the hardenable composition can affect paste time and working time, the invention is not limited to any particular molecular weight. However, the molecular weight (Mw) of the emulsion polymerized particles may range from 25,000 to 3,000,000, while the molecular weight of other types of polymer particles may range from 25,000 to 2,000,000. In any event, the molecular weight reduction and/or particle size increase of other acrylic polymer particles can be used to increase the working time of the hardenable composition.

The first component of the acrylic polymer composition of the present invention may be independently provided in the form of a dry powder with or without the addition of a filler to be used later as a hardenable composition. Thus, in accordance with another aspect of the present invention, there is provided a powder (preferably dry powder) composition comprising a first type of acrylic polymer particles, characterized in that each of the first type of acrylic polymer particles is polymerized by a coalescence emulsion A network of acrylic particles and optionally, at least one other type of acrylic polymer particles blended with the particles.

Preferably, the emulsion composition of the powder composition is in its polymer matrix with a suitable initiator compound which, in the case of multistage emulsion particles, is incorporated into its outer shell in the final stage.

Embodiments of the present invention will now be described with reference to the accompanying examples and referring to the drawings.

Instance

Emulsion polymerization and spray drying are used to produce PMMA having a large proportion of PMMA particles formed from coalesced emulsion polymerized particles.

Example 1 Emulsion polymerization

1.0 liter of deionized water was added to a 5 liter round bottom glass flask equipped with a nitrogen inlet, a condenser, and an electrically operated stainless steel paddle stirrer. The water was heated to 82 ° C by means of an electric heating mantle while stirring at 392 min ^-1 . A stream of nitrogen was passed through the vapor space above the surface of the liquid in the flask.

Prepared from 500 g of methyl methacrylate (containing 5ppm Topanol A inhibitor) and 5.0 grams of 75% active dioctyl sulfosuccinate emulsifier (trade name: Aerosol ^TM OT) a monomer mixture composed of. Mix these ingredients before use.

Polymer seed crystals (stage 1) were prepared by adding 50 grams of the monomer mixture to the flask at a water temperature of 82 ° C followed by the addition of 10 ml of a 2% by weight potassium persulfate solution in deionized water. After a slight exotherm, the reaction was allowed to proceed for 30 minutes until the temperature returned to 82 °C.

The nucleus was then grown on the polymer seed particles by first adding 20 ml of a 2% by weight potassium persulfate solution in deionized water to the flask, followed by continuous addition of 350 gram of monomer mixture over a period of about 35 minutes using a peristaltic pump. (Phase 2). After the addition of the monomer mixture was completed, the reaction was further carried out for 15 minutes until the temperature returned to 82 °C.

Immediately prior to use, 7.0 grams of 70% active benzamidine peroxide was dissolved in the remaining 100 grams of monomer mixture at room temperature of 20-23 °C. This produces about 1% by weight of residual dibenzoguanidine (BPO) content in the polymer.

Then, the BPO-containing shell was grown by first adding 5 ml of a 2% by weight potassium persulfate solution in deionized water to the flask, followed by continuously adding a monomer mixture containing the added BPO for about 10 minutes using a peristaltic pump. Nuclear (phase 3). After all monomer mixtures had been added, the reaction was allowed to proceed for an additional 15 minutes until the temperature had returned to 82 °C.

The resulting emulsion was then cooled to below 40 ° C and filtered through a 150 micron sieve.

The Z average emulsion particle size was determined using a Malvern Zetasizer Nano Series S Particle Size Analyzer.

Spray drying

By using a laboratory spray dryer LabPlant ^TM SD05 spray dried emulsion separated in powder form. The inlet temperature was 135 ° C, the latex feed rate was set to 15, the 1.0 mm nozzle size was used and the maximum setpoint of air flow rate and air compressor pressure were used.

The resulting powder was characterized: particle size (d10, d50, d90) as measured by a Malvern Mastersizer 2000 particle size analyzer; the ratio of spray dried powder having a particle size of less than 20 microns and less than 10 microns, measured by a Malvern Mastersizer 2000; Moisture content (% by weight), measured by Karl Fischer titration; comparative viscosity (RV) (dl/g), measured in chloroform (1% by weight solution); molecular weight, infiltrated by gel Chromatography (GPC) measurement; and residual dibenzoyl peroxide content (% by weight), measured by titration.

D10, d50, and d90 are standard "percentile" readings from particle size analysis.

A sample with a d50 of 50% is smaller than it and 50% is larger than its size, in microns.

D10 is a particle size at which 10% of the sample size is below.

D90 is 90% of the sample size below which the sample size is below.

The characterization results are listed in Table 1.

Example 2

As in Example 1, but using 14.0 grams of 70% active benzamidine peroxide and the stirrer speed was reduced to 300 min ^-1 .

Example 3

As in Example 2, about 1.0 gram of 1-dodecanethiol was added to the initial monomer mixture to reduce the molecular weight of the polymer prior to initiating the polymerization.

Example 4

As in Example 3, the 1-dodecanethiol content was increased to 2.0 grams to further reduce the molecular weight of the polymer.

Example 5

As in Example 4, but in stage 3, 21.0 grams of 70% active benzamidine peroxide was used.

Example 6

As in Example 3, the batch was doubled and the reaction temperature was lowered to 80 °C.

Example 7

As in Example 6, but the 1-dodecanethiol content was reduced from 2.0 grams to 1.85 grams to increase the molecular weight of the polymer, and the amount of 70% active benzamidine added in the third stage was increased from 28 grams to 30 grams. The gram is added to increase the amount of residual benzamidine peroxide in the obtained emulsion-polymerized fine particles.

Example 8 Emulsion polymerization (using emulsified monomer feed)

1.5 liters of deionized water was added to a 5 liter round bottom glass flask equipped with a nitrogen inlet, a condenser, and an electrically operated stainless steel paddle stirrer. The water was heated to 80 ° C by means of an electric heating jacket while stirring at 390 min ^-1 . A stream of nitrogen was passed through the vapor space above the surface of the liquid in the flask.

Prepared from 1000 grams of methyl methacrylate (containing 5 ppm Topanol A inhibitor), 1.85 grams of 1-dodecanethiol, 10.0 grams of 75% dioctyl sulfosuccinate emulsifier (trade name: Aerosol ^TM OT And an emulsified monomer mixture consisting of 0.5 liters of deionized water. This mixture was stirred before the addition and throughout the addition to keep it emulsified.

Polymer seed crystals (stage 1) were prepared by adding 162.5 grams of monomer mixture to the flask at a water temperature of 80 ° C followed by the addition of 10 ml of a 2% by weight potassium persulfate solution in deionized water. After a slight exotherm, the reaction was allowed to proceed for 30 minutes until the temperature returned to 80 °C.

The nucleus was then grown on the polymer seed particles by first adding 20 ml of a 2% by weight potassium persulfate solution in deionized water to the flask, followed by continuous addition of 1147.5 grams of the emulsified monomer mixture over a period of about 135 minutes using a peristaltic pump. On (the second stage). After the addition of the monomer mixture was completed, the reaction was further carried out for 15 minutes until the temperature returned to 80 °C.

Prior to use, 30.0 grams of 70% active benzamidine peroxide was dissolved in the remaining 200 grams of emulsified monomer mixture at room temperature of 20-23 °C.

The shell containing BPO was then grown by first adding 10 ml of a 2% by weight potassium persulfate solution in deionized water to the flask, followed by continuous addition of the emulsified monomer mixture containing the added BPO over a period of about 24 minutes using a peristaltic pump. On the nuclear (stage 3). After all monomer mixtures had been added, the reaction was allowed to proceed for an additional 15 minutes until the temperature had returned to 80 °C.

The resulting emulsion was then cooled to below 40 ° C and filtered through a 150 micron sieve.

The Z average emulsion particle size was measured using a Malvern Zetasizer Nano Series S particle size analyzer and the emulsion was spray dried using the same method as in Example 1.

Example 9

As in Example 8, but operating at a stirrer speed of 300 min ^-1 and adding an emulsified monomer mixture in the second stage over 90 minutes.

Example 10

A batch of emulsion was prepared according to Example 6 and was recovered in powder form using coacervation instead of spray drying as follows: A solution of 100 grams of magnesium sulfate heptahydrate in 2 liters of deionized water was heated to 80 ° C with stirring at 600 rpm. 1000 g of the emulsion prepared as in Example 6 was added to the solution using a peristaltic pump at a flow rate of about 33 g/min. After the end of the addition, the resulting mixture was kept for 5 minutes and then cooled to 40 °C. The polymer was then filtered, washed with deionized water and dried to dryness in an oven at 60 °C.

The polymer has a particle size (d50) of 183 μm and a molecular weight (Mw) of about 476,000 Daltons.

Example 11

This example describes the blending of spray dried emulsion polymers with conventional PMMA beads.

A common laboratory scale method of blending spray dried PMMA powder with conventional PMMA beads is to use flip blending in a suitable container. The container is typically filled to three-quarters of the total volume and the blending time is typically from 15 to 30 minutes.

Starting PMMA bead polymer ( B866, available from Lucite International Speciality Polymers & Resins Limited, has an RV of 2.4 dl/g, a Mw of 421,200, a residual BPO of 2.94% by weight, an average particle size of 39 microns and a d50 of 44 microns. This was blended with the spray dried PMMA powder prepared according to the method of Example 7 in different ratios.

The blend was then mixed with the MMA monomer containing 60 ppm HQ inhibitor at a ratio of 20 g polymer: 10 ml monomer at 20 ° C and the paste time and working time were measured. The two components were equilibrated in an incubator for at least 10 hours at 20 °C prior to mixing. The desired amount of polymer is then placed in a polypropylene beaker followed by the placement of the monomer. The timing begins when the powder is added to the liquid. Manual mixing was then carried out using a metal spatula for 30 seconds, then the material was covered and allowed to stand. The consistency of the material is periodically assessed and the time of maturity and working time are determined. Table 2 records the results.

Table 2 shows how increasing the amount of spray dried emulsion powder in the blend significantly shortens the paste ripening time. In addition, quick maturing time can be achieved without significantly reducing working hours.

Example 12

Example 11 was repeated except that the liquid component was MMA containing 60 ppm HQ inhibitor and 1% DMPT accelerator. Table 3 records the results.

A comparison of Table 3 with Table 2 shows that the addition of DMPT accelerator to the liquid significantly reduces the working time, but has no significant effect on the paste time.

Example 13

This example compares the operational properties of polymer blends prepared from emulsion polymers recovered in powder form by different methods (spray drying and coacervation). Further, as a comparative example, the operational properties of the sieved PMMA bead polymer and the ball milled PMMA polymer are also shown.

The PMMA emulsion was recovered in powder form in a different manner, i.e., (i) a spray-dried emulsion polymer according to the method of Example 1, and (ii) a coagulated emulsion prepared according to the method of Example 10. The dried PMMA emulsion powders (i) and (ii) were then blended with PMMA beads at a ratio of 15% by weight dried PMMA emulsion powder: 85% by weight PMMA beads. PMMA bead polymer is B866, available from Lucite International Speciality Polymers & Resins Limited. It had an RV of 2.4 dl/g, a Mw of 421,200, a residual BPO of 2.94% by weight, an average particle size of 39 microns and a d50 of 44 microns.

Two comparative examples were prepared, namely, (iii) a PMMA bead polymer (RV 2.1) via a 38 micron mesh screen ( TS1890, obtained from Lucite International Speciality Polymers & Resins Limited, was sieved and retained through the sieve powder. The resulting graded powder was then used without further treatment. It has an average particle size of 15 microns and a d50 of 15 microns. The amount of particles smaller than 20 microns was 70.6%. By using PMMA bead polymer ( B866, obtained from Lucite International Speciality Polymers & Resins Limited, was ball milled for 28 hours to prepare other comparative examples (iv). This sample was used directly from a ball mill without further processing.

Also selected from Lucite International Speciality Polymers & Resins Limited The B866 control sample was tested as the sole powder component. This sample and samples (i) to (iv) were then mixed with MMA monomer containing 60 ppm HQ at a ratio of 20 g polymer: 10 ml monomer at 20 ° C and the paste time and working time were measured. All materials were equilibrated in an incubator for at least 10 hours at 20 °C prior to mixing. The desired amount of polymer is then placed in a polypropylene beaker followed by the placement of the monomer. The timing begins when the powder is added to the liquid. Manual mixing was then carried out using a metal spatula for 30 seconds, then the material was covered and allowed to stand. The consistency of the material was periodically evaluated and the paste time, working time and setting time were determined. Table 4 records the results.

Table 4 shows that both PMMA powders containing emulsion microparticles (i) and (ii) have similar maturing times, regardless of how they are prepared. In addition, these powders still retain the relatively long working time of the control sample. This is in contrast to Comparative Example (iii) having a high fraction of less than 20 micron particles separated by a sieving method. In this case, increasing the amount of particles smaller than 20 μm allows the bake time to be moderately shortened, but this has another disadvantage of shortening the working time. The potency of samples (i) and (ii) was also compared to ball milled PMMA (Comparative Example (iv)) having a fast agglomeration characteristics similar to the powder of the emulsion polymer. However, sample (iv) has the disadvantage of a much shorter working time.

Example 14

This example shows the effect of the residual peroxide content of the spray dried PMMA emulsion powder on the handling properties.

PMMA bead polymer ( B866, available from Lucite International Speciality Polymers & Resins Limited, has an RV of 2.4 dl/g, a Mw of 421,200, a residual BPO of 2.94% by weight, an average particle size of 39 microns and a d50 of 44 microns.

All polymer blends contained 85% by weight of PMMA beads and 15% by weight of spray-dried PMMA powder, which differed in the amount of benzoic acid peroxide contained in the shell of the PMMA emulsion. The blends were then mixed with MMA monomer containing 60 ppm HQ inhibitor and 1% DMPT accelerator at 20 ° C in a ratio of 20 g polymer: 10 ml monomer and the paste time and working time were measured. The two components were equilibrated in an incubator for at least 10 hours at 20 °C prior to mixing. The desired amount of polymer is then placed in a polypropylene beaker followed by the placement of the monomer. The timing begins when the powder is added to the liquid. Manual mixing was then carried out using a metal spatula for 30 seconds, then the material was covered and allowed to stand. The consistency of the material was periodically evaluated and the paste time, working time and setting time were determined. Table 5 records the results.

Table 5 shows that the amount of residual BPO has a minimal effect on the paste ripening time, but the increase in the amount causes the solidification time and working time to be shortened.

Example 15

Contrast viscosity (RV) is a suitable measure of molecular weight. This example shows the effect of the RV of the spray dried PMMA emulsion powder on the handling properties.

PMMA bead polymer ( B866, available from Lucite International Speciality Polymers & Resins Limited, has an RV of 2.4 dl/g, a Mw of 421,200, a residual BPO of 2.94% by weight, an average particle size of 39 microns and a d50 of 44 microns.

All polymer blends contained 85 wt% PMMA beads and 15 wt% spray dried PMMA powder. The blends were then mixed with MMA monomer containing 60 ppm HQ inhibitor at a ratio of 20 g polymer: 10 ml monomer at 20 ° C and the paste time and working time were measured. The two components were equilibrated in an incubator for at least 10 hours at 20 °C prior to mixing. The desired amount of monomer is then placed in a polypropylene beaker followed by the placement of the polymer powder. The timing begins when the powder is added to the liquid. Manual mixing was then carried out using a metal spatula for 30 seconds, then the material was covered and allowed to stand. The consistency of the material was periodically evaluated and the paste time, working time and setting time were determined. Table 6 records the results.

Table 6 shows that higher RV (higher molecular weight) promotes shorter paste ripening times.

Example 16

Example 15 was repeated except that the liquid component was MMA containing 60 ppm HQ inhibitor and 1% DMPT accelerator. Table 7 records the results.

A comparison of Table 7 with Table 6 shows that the addition of DMPT accelerator to the liquid significantly reduces the working time, but has no significant effect on the maturing time.

Example 17

This example shows the effect of DMPT accelerator on the nature of the operation.

PMMA bead polymer ( B866, available from Lucite International Speciality Polymers & Resins Limited, has an RV of 2.4 dl/g, a Mw of 421,200, a residual BPO of 2.94% by weight, an average particle size of 39 microns and a d50 of 44 microns.

The spray dried PMMA powder had an RV of 2.4 dl/g and a residual BPO of 1.98 wt% and was prepared following the procedure of Example 7, wherein the amount of 1-dodecanethiol in the monomer mixture relative to the total monomer Reduced from 0.185% w/w to 0.0867% w/w to achieve a higher RV. All subsequent polymer blends contained 85% by weight PMMA beads and 15% by weight spray dried PMMA powder.

The MMA monomer contains 60 ppm HQ inhibitor and an amount of DMPT accelerator varying between 0.25 wt% and 1.5 wt%.

The blend was mixed with the monomer at a ratio of 20 g of polymer: 10 ml of monomer at 20 ° C and the paste time, working time and set time were measured. The two components were equilibrated in an incubator for at least 10 hours at 20 °C prior to mixing. The desired amount of monomer is then placed in a polypropylene beaker followed by the placement of the polymer powder. The timing begins when the powder is added to the liquid. Manual mixing was then carried out using a metal spatula for 30 seconds, then the material was covered and allowed to stand. The consistency of the material was periodically evaluated and the paste time, working time and setting time were determined. Table 8 records the results.

Table 8 shows that the amount of DMPT accelerator has minimal effect on paste time, but the increase in volume results in shorter working hours and set times.

Examples 18 and 19 illustrate how the Z average particle size of the emulsion polymerized microparticles can be varied.

Example 18

This example shows a relatively large emulsion particles of Z-average particle size may be reduced by dioctyl sodium sulfosuccinate emulsifier (trade name: Aerosol ^TM OT) is used in an amount to achieve.

2.0 liters of deionized water was added to a 5 liter round bottom glass flask equipped with a nitrogen tube, a condenser, and an electrically operated stainless steel paddle stirrer. The water was heated to 80 ° C by means of an electronically controlled electric heating mantle while stirring at 300 min ^-1 . A stream of nitrogen was passed through the vapor space above the surface of the liquid in the flask.

Monomer mixture consisting of 1000 grams methyl methacrylate (containing 5ppm Topanol A inhibitor), 1.85 grams of 1-dodecanethiol and 1.34 grams of 75% active Aerosol ^TM OT of the composition.

When the water temperature has stabilized at 80 ° C, polymer seed crystals are prepared by adding 100 grams of monomer mixture to the flask followed by 10 ml of a 2% by weight potassium persulfate solution in deionized water (Phase 1) . The resulting polymerization exotherm was quenched (about 30 minutes) and the temperature of the reactor contents was returned to 80 °C.

The polymer core was then grown on the polymer seed by first adding 20 ml of a 2% by weight potassium persulfate solution in deionized water to the flask, followed by continuous addition of 700 g of the monomer mixture over a period of about 75 minutes using a peristaltic pump. On the particle (stage 2). After the addition of the monomer mixture was completed, the reaction was further carried out for 15 minutes at a temperature set to 80 °C.

Prior to use, 28.0 grams of 75% active benzamidine peroxide (BPO) was dissolved in the remaining 200 grams of monomer mixture at room temperature of 20-23 °C.

The shell containing BPO was then grown by first adding 10 ml of a 2% by weight potassium persulfate solution in deionized water to the flask, followed by continuous addition of the remaining monomer mixture containing the added BPO over a period of about 25 minutes using a peristaltic pump. On the nuclear (stage 3). After the addition of the monomer mixture was completed, the reaction was further carried out for 15 minutes at a temperature set to 80 °C.

The resulting emulsion was then cooled to below 40 ° C and filtered through a 150 micron sieve. The Z average particle size of the resulting emulsion was measured using a Malvern Zetasizer Nano Series S particle size analyzer and was measured to be 437 nm.

The emulsion was isolated and characterized in powder form by spray drying using the method of Example 1: particle size (d10, d50, d90) as measured by a Malvern Mastersizer 2000 particle size analyzer; comparative viscosity (RV) (dl/ g), measured in chloroform (1% by weight solution); molecular weight, measured by gel permeation chromatography (GPC); and residual benzamidine peroxide content (% by weight), measured by titration.

D10, d50, and d90 are standard "percentile" readings from particle size analysis.

A sample with a d50 of 50% is smaller than it and 50% is larger than its size, in microns.

D10 is a particle size at which 10% of the sample size is below.

D90 is 90% of the sample size below which the sample size is below.

The characterization results are listed in Table 10.

Example 19

This example shows that a relatively small Z average particle size can be achieved by increasing the amount of monomer used to make the seed crystal (stage 1) and reducing the amount of monomer used to form the core (stage 2).

2.0 liters of deionized water was added to a 5 liter round bottom glass flask equipped with a nitrogen tube, a condenser, and an electrically operated stainless steel paddle stirrer. The water was heated to 80 ° C by means of an electronically controlled electric heating mantle while stirring at 300 min ^-1 . A stream of nitrogen was passed through the vapor space above the surface of the liquid in the flask.

Monomer mixture consisting of 1000 grams methyl methacrylate (containing 5ppm Topanol A inhibitor), 1.85 grams of 1-dodecanethiol and 10.0 grams of 75% active Aerosol ^TM OT of the composition.

When the water temperature has stabilized at 80 ° C, polymer seed crystals are prepared by adding 250 gram of monomer mixture to the flask followed by 20 ml of 2% by weight potassium persulfate solution in deionized water (Phase 1) . The resulting polymerization exotherm was quenched (about 30 minutes) and the temperature of the reactor contents was returned to 80 °C.

The polymer core was then grown on the polymer seed by first adding 15 ml of a 2% by weight potassium persulfate solution in deionized water to the flask, followed by continuous addition of 550 grams of monomer mixture over a period of about 60 minutes using a peristaltic pump. On the particle (stage 2). After the addition of the monomer mixture was completed, the reaction was further carried out for 15 minutes at a temperature set to 80 °C.

Prior to use, 28.0 grams of 75% active benzamidine peroxide (BPO) was dissolved in the remaining 200 grams of monomer mixture at room temperature of 20-23 °C.

The shell containing BPO was then grown by first adding 10 ml of a 2% by weight potassium persulfate solution in deionized water to the flask, followed by continuous addition of the remaining monomer mixture containing the added BPO over a period of about 25 minutes using a peristaltic pump. On the nuclear (stage 3). After the addition of the monomer mixture was completed, the reaction was further carried out for 15 minutes at a temperature set to 80 °C.

The resulting emulsion was then cooled to below 40 ° C and filtered through a 150 micron sieve.

The resulting emulsion had a Z average particle size of 165 nm (see Table 10).

The emulsion was isolated in powder form by spray drying using the method of Example 1 and characterized according to Example 18. The characterization results are listed in Table 10.

Examples 20-23 illustrate how the amount of initiator remaining in the emulsion polymerized microparticles can be varied.

Example 20

2.0 liters of deionized water was added to a 5 liter round bottom glass flask equipped with a nitrogen tube, a condenser, and an electrically operated stainless steel paddle stirrer. The water was heated to 80 ° C by means of an electronically controlled electric heating mantle while stirring at 300 min ^-1 . A stream of nitrogen was passed through the vapor space above the surface of the liquid in the flask.

Monomer mixture consisting of 1000 grams methyl methacrylate (containing 5ppm Topanol A inhibitor), 1.85 grams of 1-dodecanethiol and 10.0 grams of 75% active Aerosol ^TM OT of the composition.

When the water temperature has stabilized at 80 ° C, polymer seed crystals are prepared by adding 100 grams of monomer mixture to the flask followed by 10 ml of a 2% by weight potassium persulfate solution in deionized water (Phase 1) . The resulting polymerization exotherm was quenched (about 30 minutes) and the temperature of the reactor contents was returned to 80 °C.

The polymer core was then grown on the polymer seed by first adding 15 ml of a 2% by weight potassium persulfate solution in deionized water to the flask, followed by continuous addition of 600 gram of monomer mixture over a period of about 65 minutes using a peristaltic pump. On the particle (stage 2). After the addition of the monomer mixture was completed, the reaction was further carried out for 15 minutes at a temperature set to 80 °C.

Immediately before use, 42.0 grams of 75% active benzamidine peroxide (BPO) was dissolved in the remaining 300 grams of monomer mixture at room temperature of 20-23 °C.

After the reactor contents have been returned to 80 ° C, the solution is then added to the flask by first adding 15 ml of a 2% by weight potassium persulfate solution in deionized water, followed by continuous addition of the added BPO over a period of about 30 minutes using a peristaltic pump. The remaining monomer mixture is such that the shell containing BPO grows on the core (stage 3). After the addition of the monomer mixture was completed, the reaction was further carried out for 15 minutes at a temperature set to 80 °C.

The resulting emulsion was then cooled to below 40 ° C and filtered through a 150 micron sieve.

The emulsion was isolated in powder form by spray drying using the method of Example 1 and characterized according to Example 18. The characterization results are listed in Table 10.

The amount of the BPO initiator remaining in the emulsion polymerization fine particles was measured to be 2.30% by weight.

Example 21

Example 20 was repeated except that in the third stage a greater amount of 75% active benzammonium peroxide (BPO) was used, i.e., 49.0 grams.

The amount of BPO initiator remaining in the emulsion polymerized microparticles was measured to be 2.50% by weight (see Table 10).

Example 22

2.0 liters of deionized water was added to a 5 liter round bottom glass flask equipped with a nitrogen tube, a condenser, and an electrically operated stainless steel paddle stirrer. The water was heated to 80 ° C by means of an electronically controlled electric heating mantle while stirring at 300 min ^-1 . A stream of nitrogen was passed through the vapor space above the surface of the liquid in the flask.

Monomer mixture consisting of 1000 grams methyl methacrylate (containing 5ppm Topanol A inhibitor), 1.85 grams of 1-dodecanethiol and 10.0 grams of 75% active Aerosol ^TM OT of the composition.

When the water temperature has stabilized at 80 ° C, polymer seed crystals are prepared by adding 100 grams of monomer mixture to the flask followed by 10 ml of a 2% by weight potassium persulfate solution in deionized water (Phase 1) . The resulting polymerization exotherm was quenched (about 30 minutes) and the temperature of the reactor contents was returned to 80 °C.

The polymer core was then grown on the polymer seed by first adding 15 ml of a 2% by weight potassium persulfate solution in deionized water to the flask, followed by continuous addition of 500 grams of monomer mixture over a period of about 55 minutes using a peristaltic pump. On the particle (stage 2). After the addition of the monomer mixture was completed, the reaction was further carried out for 15 minutes at a temperature set to 80 °C.

Prior to use, 67.0 grams of 75% active benzamidine peroxide (BPO) was dissolved in the remaining 400 grams of monomer mixture at room temperature of 20-23 °C.

After the reactor contents have been returned to 80 ° C, the solution is then added to the flask by first adding 15 ml of a 2% by weight potassium persulfate solution in deionized water, followed by continuous addition of the added BPO over a period of about 30 minutes using a peristaltic pump. The remaining monomer mixture is such that the shell containing BPO grows on the core (stage 3). After the addition of the monomer mixture was completed, the reaction was further carried out for 15 minutes at a temperature set to 80 °C.

The resulting emulsion was then cooled to below 40 ° C and filtered through a 150 micron sieve.

The emulsion was isolated in powder form by spray drying using the method of Example 1 and characterized according to Example 18. The characterization results are listed in Table 10.

The amount of the BPO initiator remaining in the emulsion polymerization fine particles was measured to be 3.05% by weight.

Example 23

2.0 liters of deionized water was added to a 5 liter round bottom glass flask equipped with a nitrogen tube, a condenser, and an electrically operated stainless steel paddle stirrer. The water was heated to 80 ° C by means of an electronically controlled electric heating mantle while stirring at 300 min ^-1 . A stream of nitrogen was passed through the vapor space above the surface of the liquid in the flask.

Monomer mixture consisting of 1000 grams methyl methacrylate (containing 5ppm Topanol A inhibitor), 1.85 grams of 1-dodecanethiol and 10.0 grams of 75% active Aerosol ^TM OT of the composition.

When the water temperature has stabilized at 80 ° C, the polymer seed crystals are prepared by adding 50 g of the monomer mixture to the flask, followed by adding 10 ml of a 2 wt% potassium persulfate solution in deionized water (Phase 1). . The resulting polymerization exotherm was quenched (about 30 minutes) and the temperature of the reactor contents was returned to 80 °C.

The polymer core was then grown on the polymer seed by first adding 15 ml of a 2% by weight potassium persulfate solution in deionized water to the flask, followed by continuous addition of 450 grams of monomer mixture over a period of about 45 minutes using a peristaltic pump. On the particle (stage 2). After the addition of the monomer mixture was completed, the reaction was further carried out for 15 minutes at a temperature set to 80 °C.

Immediately before use, 100.0 grams of 75% active benzamidine peroxide (BPO) was dissolved in the remaining 500 grams of monomer mixture at room temperature of 20-23 °C.

After the reactor contents had been returned to 80 ° C, the solution was first added to the flask by first adding 15 ml of a 2% by weight potassium persulfate solution in deionized water, followed by continuous addition of BP0 containing the addition over a period of about 30 minutes using a peristaltic pump. The remaining monomer mixture is such that the shell containing BPO grows on the core (stage 3). After the addition of the monomer mixture was completed, the reaction was further carried out for 15 minutes at a temperature set to 80 °C.

The resulting emulsion was then cooled to below 40 ° C and filtered through a 150 micron sieve.

The emulsion was isolated in powder form by spray drying using the method of Example 1 and characterized according to Example 18. The characterization results are listed in Table 10.

The amount of the BPO initiator remaining in the emulsion polymerization fine particles was measured to be 4.50% by weight.

Example 24

This example shows the effect of the residual peroxide content of the spray dried PMMA emulsion powder on the handling properties and extends the range shown in Example 14.

PMMA bead polymer ( B866, available from Lucite International Speciality Polymers & Resins Limited, has an RV of 2.4 dl/g, a Mw of 421,200, a residual BPO of 2.94% by weight, an average particle size of 39 microns and a d50 of 44 microns.

All polymer blends contained 85% by weight of PMMA beads and 15% by weight of spray-dried PMMA powder, which differed in the amount of benzoic acid peroxide contained in the shell of the PMMA emulsion. The blends were then mixed with MMA monomer containing 60 ppm HQ inhibitor and 1% DMPT accelerator at 20 ° C in a ratio of 20 g polymer: 10 ml monomer and the paste time and working time were measured. The two components were equilibrated in an incubator for at least 10 hours at 20 °C prior to mixing. The desired amount of polymer is then placed in a polypropylene beaker followed by the placement of the monomer. The timing begins when the powder is added to the liquid. Manual mixing was then carried out using a metal spatula for 30 seconds, then the material was covered and allowed to stand. The consistency of the material was periodically evaluated and the paste time, working time and setting time were determined. Table 9 records the results.

Table 9 shows that the amount of residual BPO has a minimal effect on the paste ripening time, but the increase in the amount causes the solidification time and working time to be shortened.

Example 25

This example illustrates the preparation of emulsion polymerized microparticles in two stages rather than three of the previous examples. The seed particles are initially formed, which then act as crystal nuclei for the combined core and shell growth.

2.0 liters of deionized water was added to a 5 liter round bottom glass flask equipped with a nitrogen tube, a condenser, and an electrically operated stainless steel paddle stirrer. The water was heated to 80 ° C by means of an electronically controlled electric heating mantle while stirring at 300 min ^-1 . A stream of nitrogen was passed through the vapor space above the surface of the liquid in the flask.

Monomer mixture consisting of 1000 grams methyl methacrylate (containing 5ppm Topanol A inhibitor), 1.85 grams of 1-dodecanethiol and 10.0 grams of 75% active Aerosol ^TM OT of the composition.

When the water temperature has stabilized at 80 ° C, polymer seed crystals are prepared by adding 100 grams of monomer mixture to the flask followed by 10 ml of a 2% by weight potassium persulfate solution in deionized water (Phase 1) . The resulting polymerization exotherm was quenched (about 30 minutes) and the temperature of the reactor contents was returned to 80 °C.

Immediately before use, 49.0 grams of 75% active benzamidine peroxide (BPO) was dissolved in the remaining 900 grams of monomer mixture at room temperature of 20-23 °C.

The polymer core and shell were then added by first adding 30 ml of a 2% by weight potassium persulfate solution in deionized water to the flask, followed by continuous addition of the remaining monomer mixture containing the added BPO over a period of about 90 minutes using a peristaltic pump. Growing on polymer seed particles (stage 2). After the addition of the monomer mixture was completed, the reaction was further carried out for 15 minutes at a temperature set to 80 °C.

The resulting emulsion was then cooled to below 40 ° C and filtered through a 150 micron sieve. The resulting emulsion had a Z average particle size of 206 nm.

The emulsion was isolated in powder form by spray drying using the method of Example 1 and characterized according to Example 18. The characterization results are listed in Table 10.

The amount of the BPO initiator remaining in the emulsion polymerization fine particles was measured to be 2.80% by weight.

SEM images of the surface of the dry powder particles of the present invention are shown in Figures 1 and 2. Figure 1 shows two images of the size and structure of spray dried emulsion polymerized microparticles. Figure 2 shows two images of the size and structure of the agglomerated and dried particles. In both cases, the dried microparticles have coalesced to form a random microporous structure of the acrylic polymer particles of the present invention. Figure 1b shows the formation of a pseudo-hexagonal dense array of spray dried emulsion particles in some areas. However, Figures 2a and 2b show that although the microporous structure of the agglomerated and dried particulate particles is indistinguishable from the spray-dried powder particles, there is no evidence of a hexagonal dense structure. The particles are not shown in the SEM image to form the discrete larger particles of the first type of the invention.

It should be noted that all articles and documents and all such articles and documents that are related to the present application in conjunction with or prior to the present specification and which are disclosed together with the present specification are incorporated herein by reference. In this article.

All of the features disclosed in this specification (including any accompanying claims, abstracts and drawings) and/or all the steps of any method or process disclosed herein may be combined in any combination, such features and/or Except for the combination of at least some of the mutually exclusive steps.

Each feature disclosed in this specification (including any accompanying claims, the abstract, and the drawings) may be replaced by alternative features that achieve the same, equivalent or similar purpose. Therefore, unless expressly stated otherwise, the disclosed features are only one example of a series of common equivalent or similar features.

The invention is not limited to the details of the above embodiments. The present invention extends to any novel feature or any novel combination of the features disclosed in the specification (including any accompanying claims, abstract and drawings), or any novel steps of the steps of any method or process disclosed herein. Or any novel combination.

Figure 1a shows an SEM image of the surface of the spray dried polymer particles of the present invention;

Figure 1b shows another SEM image of the same type of particles as Figure 1a;

Figure 2a shows an SEM image of the surface of the coagulated and dried polymer particles of the present invention;

Figure 2b shows another SEM image of the same type of particles as Figure 2a.

(no component symbol description)

Claims (28)

A hardenable two-component acrylic composition comprising a first component of an acrylic polymer composition and a second component of an acrylic monomer composition, the acrylic polymer composition comprising a first type of acrylic polymer particles, characterized in that Each of the first type of acrylic polymer particles is formed from a network of coalesced emulsion-polymerized acrylic microparticles, wherein the coalesced emulsion polymerized microparticle network forms porous acrylic polymer particles, and the first type of acrylic polymer therein The particles have an average particle size of from 1 to 300 microns. The hardenable two-component acrylic composition of claim 1, wherein the acrylic polymer composition further comprises at least one other type of acrylic polymer particles. The hardenable two-component acrylic composition of claim 2, wherein the at least one other type of acrylic polymer particles are polymer beads. The hardenable two-component acrylic composition of claim 1, 2 or 3, wherein the emulsion-polymerized microparticles have a Z average particle size of less than 2000 nm. The hardenable two-component acrylic composition of claim 4, wherein the emulsion-polymerized microparticles have a Z average particle size of between 10 and 2000 nm. The hardenable two-component acrylic composition of claim 1, 2 or 3, wherein the emulsion-polymerized microparticles are single-stage or multi-stage core/shell microparticles. The hardenable two-component acrylic composition of claim 1, 2 or 3 wherein the emulsion microparticles are in their polymer matrix and have an unreacted initiator. The hardenable two-component acrylic composition of claim 7, wherein the unreacted initiator is present in an amount of 0.001 of the emulsion-polymerized acrylic microparticles. 10.0% w/w. The hardenable two-component acrylic composition of claim 7, wherein the microparticles are core/shell microparticles and the unreacted initiator is incorporated into the outer shell of the core/shell particles. The hardenable two-component acrylic composition of claim 1, wherein the acrylic polymer particles are microporous. A hardenable two-component acrylic composition according to claim 1, 2 or 3, wherein the acrylic polymer particles of the first type of the invention are formed by drying a liquid emulsion to form a powder. The hardenable two-component acrylic composition of claim 11, wherein the drying is carried out by spray drying, paddle drying, drying or coagulation, and drying after filtration. The hardenable two-component acrylic composition of claim 1, 2 or 3, wherein the emulsion microparticles have a weight average molecular weight (Mw) of between 25,000 daltons and 3,000,000 daltons. A hardenable two-component acrylic composition comprising a first component of an acrylic polymer composition and a second component of an acrylic monomer composition, the acrylic polymer composition comprising acrylic polymer particles, wherein at least a first type of acrylic acid The polymer particles are microporous. The hardenable two-component acrylic composition of claim 14, wherein the acrylic polymer composition comprises emulsion polymerized acrylic polymer particles having a particle size between 10 nm and 2000 nm. A method of making an acrylic polymer composition comprising the steps of: (a) subjecting the acrylic monomer composition to emulsion polymerization to produce a polymer emulsion; (b) drying the polymer emulsion of step (a) to produce a hardenable double group as contained in any one of claims 1 to 15. The acrylic polymer particles in the acrylic composition; and (c) mixing the acrylic polymer particles of step (b) with at least one other type of acrylic polymer particles and/or filler, as appropriate, to produce An acrylic polymer composition which is hardened at a predetermined rate in the presence of an acrylic monomer composition. The method of claim 16, wherein the step (a) comprises a seed emulsion polymerization step, a core emulsion polymerization step, and at least one shell emulsion polymerization step. The method of claim 16 or 17, wherein the excess initiator is introduced into the emulsion polymerization step (a) to encapsulate the residual initiator within the emulsion particles. The method of claim 18, wherein the excess initiator is introduced at a late stage in the emulsion polymerization to avoid thermal decomposition prior to encapsulation in the formed polymer particles. The method of claim 18, wherein the excess initiator is added together with and/or after at least a portion of the initiator to be reacted with the monomer in the emulsion polymerization step. The method of claim 18, wherein at least some of the initiator to be reacted in the emulsion polymerization step is different from the excess initiator and has a shorter half-life, thereby preferentially reacting with the monomer in the presence of the excess initiator. The method of claim 18, wherein in the multistage emulsion polymerization, the excess initiator is introduced in the final stage to cause it to exist outside of the multistage particles. In the shell. A bone cement composition comprising the hardenable two-component acrylic composition of any one of claims 1 to 15. A composition for dental use comprising the hardenable two-component acrylic composition of any one of claims 1 to 15. An adhesive comprising the hardenable two-component acrylic composition of any one of claims 1 to 15. A building material comprising the hardenable two-component acrylic composition of any one of claims 1 to 15. A powder composition for use as a first component of a hardenable two-component acrylic composition comprising a first type of acrylic polymer particles characterized in that each of the first types of acrylic polymer particles is polymerized by a coalescence emulsion A network of acrylic microparticles and optionally, at least one other type of acrylic polymer particles blended with the microparticles, wherein the first type of acrylic polymer particles have an average particle size of from 1 to 300 microns. The powder composition of claim 27, wherein the emulsion particles of the powder composition are in their polymer matrix and have a suitable initiator compound.